Define XUSER_MAX_COUNT for those who don't have the DirectX SDK

Windows/XinputDevice.cpp

@@ -3,6 +3,10 @@
 #include <limits.h>
 #include <iostream>
 
+#ifndef XUSER_MAX_COUNT
+#define XUSER_MAX_COUNT 4
+#endif
+
 XinputDevice::XinputDevice() {
 	ZeroMemory( &this->prevState, sizeof(this->prevState) );
 	this->check_delay = 0;